I've been a long-time RTM user, but desperately wanted a native blackberry client appt. There are so many things to like about TD (ability add/retrieve tasks by email, iGoogle widget, flexible sorting systems, shortcut keys, default views, jott integration, etc.). So much that one could even overlook some things it lacks (autocomplete tags, saveable smart searches)
Lacking multi-edit without search, IMO, is the achilles heal of TD. It requires too much of work to change dates of tasks, change tags, move to different lists - that I cant bring myself to switch.